It is known to put one or more identifying marks on contact lenses. Identifying marks have been disclosed as useful for indicating which contact lens goes into which eye, the top and the bottom of a contact lens, or the back or the front surfaces of a contact lens. Identifying marks have been disclosed as useful for indicating serial numbers, lot and batch numbers, and optical powers. Identifying marks can also be used by optometrists to measure the rotation of a contact lens on the eye, and identifying marks can be used to orient contact lenses by quality control personnel for inspection purposes.
An identifying mark can be a letter e.g., "A," a number, e.g., "3," a symbol, e.g., "*," a trademark, e.g. "Acuvue.RTM.," and a geometric shapes, e.g., ".quadrature.," and a homogeneous or heterogeneous group of the one or more of the proceeding list, e.g., "123," and "#A1." The term "identifying mark" is used herein according to this definition.
The prior art discloses many ways to make identifying marks including laser etching and burning as taught in EP 291459 and JP 61223820, and diamond point engraving as disclosed in DE 3316730. Printing techniques, some of which use photosensitive materials which are subjected to UV radiation, are disclosed in GB 200614, DE 3219890, and JP 61211382. Other coloring and dying techniques are disclosed in JP 62186221, JP 2186222, and JP 62250286.
U.S. Pat. No. 5,467,149 discloses that the visibility of an identifying mark cut into an optically clear surface can be improved by making the mark consist of a pattern of regions of varying depth within the boundary of the mark. This patent discloses a mark consisting of stripes cut into the surface of the contact lens, such that the stripes provide a profile having a bottom which is parallel to the surface of the contact lens and sides which are normal to the surface of the contact lens.
DE 3316730 discloses numbering on a soft contact lens consisting of dots which are made by pressing a rounded diamond tip into the contact lens.
U.S. Pat. No. 5,062,701 discloses that lines on a contact lens which are used to measure the rotation of an asymmetric lens can be made up of dots. The preferred method of forming the dots is by using a dye; however within the specification, it states that any of the line segments disclosed in the patent can be formed by laser etching or by lightly abrasive etching.
There still remains a need to improve the visibility of the identifying marks on contact lenses for the user, while still retaining an acceptable comfort level of the marked contact lenses, and keeping the mark small enough so others do not notice the mark when the contact lens is in the eye of the contact lens wearer.